Method and apparatus for digesting fibrous material



Feb. 11, 1958 A. D. MERRILL METHOD AND- APPARATUS FOR DIGESTING FIBROUSMATERIAL Filed Oct. 27, 1950 kmwkgX M E INVENTOR [LEE/PTLVIERR/LL,

BY 61. w m

ATTORNEY United States Patent METHOD AND APPARATUS FOR DIGESTING FIBROUSMATERIAL Albert l). Merrill, WatertoWn, N. Y., assignor to ChemipnlpProcess, Inc., Watertown, N. Y.

Application October 27, 1950, Serial No. 192,547

8 Claims. (Cl. 92--11) The present invention relates to a method andapparatus for digesting fibrous cellulose material and more particularlypertains to improvements in hot acid systems employed in the productionof pulp.

it has been the practice in the past in the normal operation of asulphite mill to release cooking liquor from the digester in order tolower the pressure therein. The side relief has in the past beendelivered through the high pressure relief line into the high pressureaccumulator. The side relief liquor contains a substantial amount oforganic matter which contaminates the cooking liquor in the highpressure accumulator. Thus when the acid in the high pressureaccumulator is subsequently used to fill the digester or otherdigesters, these organic elements were carried into the next cook. Thecooking acid containing material amounts of organic matter providesimpure acid and is detrimental to subsequent cooking. Such contaminatedcooking liquor tends to reduce the quality factor of the pulp such asthe tearing strength, the folding endurance and the bursting strength.in addition, the cooking liquor contaminated by the organic matter alsotends to reduce the yield of pulp and the system requires more sulphurto properly cook a given quantity of cellulosic material. In the past ithas been necessary to periodically empty and flush out the high pressureaccumulator and such steps have been required on the average of: severaltimes during each year of normal operation.

An object of the present invention, therefore, is to provide an improvedmethod of handling the side relief to prevent the accumulation oforganic matter as well as water solubles in the accumulator to therebypreserve the acid strength and to provide for an increased yield ofhigher quality pulp.

Another object of the invention is to provide apparatus for deliveringthe side relief from the digester into a side relief storage tank asdistinguished from the accumulator to thereby avoid contamination of thecooking liquor and at the same time to. employ the side relief liquor asa continuous spray in a degassing tower under pressure so as to removeand reclaim substantially all of the free sulphur dioxide contained inthe side relief and to thereby provide a saving in the sulphur requiredfor each unit of pulp cooked.

A still further object of the invention is to provide apparatus fortransferring the heat units of the side relief liquor and gas to thefortified acid entering the system and to deliver the cooled gases to arecoverytower for absorption in the raw acid supply.

Other and equally important; objects of the; invention will be apparentand appreciated by those skilledin the art as the present disclosureproceeds and upon consideration of the acompanying drawing and thefollowing detailed description wherein an exemplary embodiment ofapparatus exhibiting. the invention and which may be employed incarrying out the process is disclosed.

The single sheet of the annexeddrawing includes a diagrammatic flowchart illustrating a system embodying the. invention and for carryingout theimproved method.

The present invention is directed to the removal of the side relieffromthe digester and provides the advantages of recovering the heat andgases contained in the side relief liquor without contaminating thecooking liquor in the high pressure accumulator with organic matter fromthe digester. The side relief is diverted from the accumulator tothereby prevent the contamination of. the acid and such a methodaccordingly prevents the degrading of thepulp and a reductionof theyield of pulp when the liquor within the accumulator is employed insubsequent cooking operations. In addition the present inventionprovides for the recovery of the heat units contained in theside reliefliquor and gases and at the same time avoids any loss of free sulphurdioxide. The principles of the invention as hereinabove expressed may bereadily appreciated from a consideration of a specific method in whichthey are embodied and apparatus in which they are adapted to beeffectuated as shown in the drawing. A system for carrying out thepresent invention may include as elements a digester 1, a high pressureaccumulator 2, a low pressure accumulator 3, a side relief storage tank4, and a degassing tower 5. The apparatus includes as further elements afortified acid storage tank 6, a recovery tower 7, a raw acid storagetank 8, a weak acid tank 9, and a tail gas absorption tower 10.

The digester 1 may be of a conventional construction and a pulp millembodying the features and principles of the present invention mayinclude a series of digesters one of which is shown in the drawing. Thedigester is provided with a conventional arrangement for admitting steamand one of such pipe connections is represented at 12 provided with avalve 14. The digester may be provided with a blow-01f elbow 16 and thehorizontal arm thereof includes a valve 17. The digester 1 may be filledwith wood chips in the usual manner and closed by a man-hole cover 18. Avent line for permitting air to escape from the digester is indicated at19 and provided with a valve 20. for closing the vent when gas begins toescape; from the digester during the filling operation.

The high pressure accumulator 2 is of a conventional construction andmay be of any desired shape. A conduit line 21 extends from the lowerportion of the high pressure accumulator 2 which is controlled by ahand-operated valve 22. A pump 23 is provided in the line 21 fordelivering acid from the high pressure-accumulator into the digester ina manner as well-known in the art. It will be understood that additionaldigesters (not shown) may be served by the liquor delivered through theline 21.

A high pressure relief line 25 extends from the top portion of thedigester 1 and this line is controlled by a manually operable valve 26.The high pressure relief line extends to a high pressure eductor 27 andthe drop leg 28 thereof is connected to the accumulator through a branchpipe 36 controlled by a valve 29. The high pressure accumulator 2 isprovided with a top vent line 31 which is controlled by an automaticallyoperated pressure relief valve 32. The vent line 31 is in opencommunication with a low pressure relief line 33 which extends from thetop of the digester 1 through a manually controlled valve 34. The lowpressure relief line 33 extends to a low pressure eductor 36.

Apparatus for carrying out the invention may include the low pressureaccumulator 3. A drop leg 37 extends from the low pressure eductor 36and is connected to the low pressure accumulator 3 through a branch pipe35. A valve 38 may be interposed in the pipe 35. A pipe line 39 extendsfrom the lower portion of the accumulator 3 and a pump 40 moves acidfrom the low pressure accumulator through the line 39 to the highpressure eductor 27. This fortified acid absorbs the gases in the highpressure line 25 and creates a partial vacuum therein to promote removalof the gases from the digester in a well-known manner. The fortifiedacid moves from the eductor 27 through the drop leg 28 into the highpressure accumulator. A vent conduit line 41 extends from the top of thelow pressure accumulator 3 and terminates in the lower portion of thefortified acid storage tank 6. An automatically operated pressure reliefvalve 42 is provided in the line 41 for controlling the escape of gasfrom the low pressure accumulator 3.

The digester is provided with a conventional type of strainer assembly(not shown) leading to a side relief line 43. The side relief line 43 iscontrolled by means of a hand-operated valve 44. In apparatus forcarrying out the present invention the side relief line 43 extends intocommunication with the side relief storage tank 4 and thus by-passes thehigh pressure accumulator 2. The present invention avoids delivery ofany of the side relief and the organic matter contained therein into thehigh pressure accumulator and the side relief is delivered into the siderelief storage tank 4 through the line 43.

A vent line 46 extends from the top of the side relief storage tank 4into open communication with the low pressure relief line 33 leadinginto the low pressure eductor 36. Any gases that are removed from theside relief liquor in the side relief storage tank 4 are thereby broughtinto contact with the fortified acid being delivered into the lowpressure accumulator 3. An automatic pressure operated valve 47 isprovided in line 46.

The side relief liquor within the storage tank 4 is delivered by a pump48 interposed in a conduit line 49 to a spray nozzle 51 mounted in theupper portion of the degassing tower 5. The degassed liquor present inthe tower is lead off through a suction conduit 52 to a pump 53 and thisdegassed liquor is forced through a pipe 54 into a heat exchanger 56.Thus the heat units remaining in the degassed liquor are transferred tothe fortified acid pumped from the tank 6 by a pump 58 and a conduitline 59, which extends through the heat exchanger 56. The degassedliquor from the tower after having given up its heat units is deliveredto waste through a pipe 61.

A heat exchanger 62 is provided through which the gases vented from thedegassing tower 5 are conveyed by a conduit or pipe 63. The fortifiedacid pumped through the line 59 moves in heat exchange relationship withthese gases to further add heat to the liquid from the fortified storagetank 6 on its way to the low pressure cductor 36. A vacuum pump 66 isprovided in a pipe line 67 leading from the heat exchanger 62 to furtherassist in removing all of the free sulphur dioxide contained in the siderelief. The gases exhausted by the vacuum pump 66 are delivered throughthe line 67 into the recovery tower 7 through the branch pipe 68.

The sulphur dioxide is absorbed in the recovery tower 7 in a manner aswell-known in the art. It will be noted here that substantially all ofthe free sulphur dioxide contained in the side relief is removed in thedegassing tower 5 and such gas is recovered in the reclamation systemand the heat thereof is also recovered and added to the fortified acidsupply. Under proper operating condittons about twenty-five toforty-three pounds of sulphur are saved per ton of pulp cooked byremoving all of the free sulphur dioxide in the degassed tower 5 and bymeans of the vacuum pump and the associated conduit system.

It will be further observed that the gases moving through the conduit 63are cooled by the heat exchanger 62 on ts passage to the vacuum pump 66and the recovery tower 7. Thus the gases are in a condition so as to bemore readily absorbed in the recovery tower 7. The heat units removedfrom these gases are transferred to the relatively cool fortified acidpassing through the hue 59 on its way to the low pressure eductor 36.The heat umts contained in the side relief liquor are transferred to thefortified acid from the st g t as the fortified acid is pumped to thelow pressure cductor 36 through the heat exchanger 56. The hot gasesvented from the digester through the lower pressure line 33 arecontacted by the fortified acid moving through the low pressure cductor36 and these gases are absorbed in the fortified acid and thetemperature of the acid being delivered into the low pressureaccumulator 3 is further increased.

The system includes the raw acid storage tank 8 into which raw acid isdelivered from the acid make-up means through a pipe 71. A pump '72delivers the raw acid from the tank 8 into the pipe line '73 whichterminates in a spray nozzle 79 mounted in the upper portion of therecovery tower 7. This recovery tower is provided with materials thereinfor facilitating the absorption of the gases in a manner well-known inthe art. The raw acid is sprayed downwardly in the tower 7 from thespray head 79 and flows downwardly through the absorption materialstherein against the counter flow of reclaimed gas entering the towerthrough the line 68. The fortified acid developed in the recovery tower7 is moved by a pump 76 into a conduit line 77 and delivered into thelower portion of the fortified acid storage tank 6 by means of adepending pipe 78.

The tail gas tower 10 is provided with an outlet for waste gases asrepresented by a pipe 81 which is controlled by a valve 82. Water inmetered quantities may be admitted to the tail gas tower it) through apipe connection 83 controlled by a valve 34. The tail gases within therecovery tower 7 are led through a conduit 86 into the lower portion ofthe tail gas tower it). These rising tail gases which have not beenabsorbed by the system acid move upwardly in the tail gas tower 10against the counter how of a small quantity of water flowing downwardlythrough the stoneware packed in the tail gas tower It and the resultingweak acid is delivered into the weak acid tank 9 through a conduitfitting 87. The tower 10 is constructed similarly to the tower 7 and thetail gases enter at the base of the tower 10. A relatively smallquantity of water is introduced through the conduit 83 into a chamber atthe top of the tower 10. This water flowing down through the absorptionmaterials is against the counter flow of the gases. The waste gases,such as carbon dioxide, nitrogen, and oxygen escape at the top of thetower 10 through the vent pipe 81. The recovery of a sulphur dioxidecomponent of the tail gases absorbed in the water moves into the weakacid tank 9. The weak acid may be delivered into the raw acid tank 8 bymeans of a pump 91 and the conduit 92.

A vent line 93 extends from the upper portion of the raw acid storagetank 8 into communication with a branch pipe 94 for leading gas into thelower portion of the recovery tower 7. Another vent line 96 extends fromthe top ofthe fortified acid storage tank 6. This line leads gas fromthe tank 6 into the pipe 94 and into the recovery tower 7. g

In operation the digester 1 is filled with wood chips and the man-holecover 18 is secured in position closing the digester. The valves 26, 34and 44 are closed. The valve 20 is opened. The pump 23 is started andthe valve 22 is opened so that acid is moved from the high pressureaccumulator into the digester 1. The acid liquor is forced into thelower section of the digester and as the level of the entering acidrises, air is progressively displaced and vented olf through the line19. As the level of the liquor rises free sulphur dioxide :or other gasbegins to move off the digester and the valve 20 is then closed and thevalve 34 is opened to admit such gases to the low pressure line 33.Since the acid forced from the high pressure accumulator 2 into thedigester is at an elevated temperature such evolved gases containavailable heat. Such heat units are absorbed by cooler acid moving intothe lower pressure accumulator 3 through the cductor 36.

As soon as the digester 1 has been filled with acid from the,accumulator 2, the high pressure relief line-25 is placed incommunication with the top of the digester by opening the valve 26. Thehot acid from the high pressure accumulator 2 is circulated through theline 21 into and through the digester 1 and back to the high pressureaccumulator 2 through the high pressure relief line 25 until thetemperatures are equalized at the top and bottom of the digester. Thecooking cycle is then initiated by admitting steam through the pipe. 12.At the initiation of' the cooking operation the relief gases are ventedat the start of the cook through the open valve 26 into the highpressure line 25 to the drop leg 28 :of the high pressure eductor 27where these gases are contacted by the acid delivered into the highpressure eductor 27 from the low pressure accumulator 3. This absorbsthe gas and reduces the pressure in the line 25 to facilitate theremoval of gases from the digester. An hour or more before thetermination of the cooking period the valve 26 is closed and the valve34 is opened and the pressure on the digester 1 is pulled down as low aspossible and to a range .of about twenty or twenty-five pounds by theuse of the low pressure relief line 33 and the low pressure eductor 36.This vented gas which includes steam moves into the low pressure eductor36 and is absorbed in the fortified acid moving into the drop leg 37.

At one interval during the cook period and normally about three or fourhours before the end of the cook, it has-been preferred to open the siderelief valve 44 and this side relief was previously permitted to enterthe high pressure relief line so that the side relief was moved into thehigh pressure. accumulator 2. Such an operation carried organic matterinto the cooking liquor within the high pressure accumulator 2. Thiscontaminated liquor in being used to fill the next digester producedinferior pulp and also reduced the yield.

As distinguished from the prior practice the present invention providesfor the delivery of the side relief into the side relief storage tank 4during the operation of lowering the pres-sure on the digester. Thuswhen the valve 44 is opened the side relief moves through the line 43into the tank 4 and bypasses the high pressure accumulator 2. Any gasreleased from the side relief liquor in the side relief storage tank 4moves through the conduit line 46 into the low pressure eductor 36 forabsorption in the acid supply moving into the low pressure accumulator3.

The side relief liquor in the storage tank 4 is delivered by the pump48' into the conduit line 49 and sprayed downwardly in the degassingtower 5. The side relief liquor in the tower is moved by the pump 53through the heat exchanger 56 to waste. The heat removed from thesiderelief liquor moving through the heat exchanger 56 is transferred to thefortified acid moving from the tank 6.

The gases released in the degassing tower 5 are led off in the conduitline 63 through the heat exchanger 62 where the heatunits :of the siderelief gases are transferred to the fortified acid moving towards thelow pressure accumulator 3. The removal of the free sulphur dioxide isfurther facilitated by the vacuum pump 66 and these cool gases move intothe lower portion .of the recovery tower 7 through the pipes 67 and 68.

Thus it will be appreciated that the organic matter withdrawn from thedigester through the side relief line does not contaminate the cookingliquor. In addition, the present invention provides for the recovery ofthe heat units in the side relief liquor and the heat units of siderelief gases. It will be further noted that all the free sulphur dioxidereleased from the side relief liquor is recovered and reclaimed.

While the invention has been described with reference to a particularhot acid system and with regard to one series of method steps, it willbe appreciated that changes may be made in the apparatus as well as theprocess of 6 producingpulp. Such changes .and others may be made withoutdeparting from the spirit and scope of the invention as set forth in theappended claims.

What I claim and desire to secure by Letters Patent is:

I. In apparatus for digesting cellulosic material, a digester, anaccumulator, means for moving cooking liquor from the accumulator intothe digester, a side relief storage tank, a conduit line extending fromthe digester from a point below the top and above the bottom thereofinto communication with the side relief storage tank, a closed degassingtower, a spray head in a top portion of said degassing tower, means forpumping liquid and the contained gases from the side relief storage tankto said spray head, a supply of acid, means for moving acid from saidsupply to the accumulator, means for transferring heat units from thegas released in the degassing tower to the acid moving towards theaccumulator, means for absorbing substantially all of the cooled gasesinthe acid supply, means for transferring heat units of the side reliefliquid to the acid supply, and means for delivering the cooled anddegassed side relief liquor to waste.

2. In apparatus for digesting fibrous material, a digester, anaccumulator, means for moving cooking liquor from the accumulator intothe digester, a side relief storage tank, a conduit line extending fromthe digester at a point below the top and above the bottom thereof intocommunication with the side relief storage tank, a closed degassingtower, a spray head in the top portion of said degassing tower, meansfor pumping liquid and contained gases from the side relief storage tankto said spray head, a supply of acid, means including a conduit line formoving acid from said supply to the accumulator, heat transferring meansin said conduit line, means including a vacuum pump moving gas releasedin the degassing tower through said heat exchange means to transfer heatto the acid moving towards the accumulator, means for absorbing thecooled gas in the acid supply, means for transferring heat units of theside relief liquid to the acid moving to the accumulator, and means fordelivering the side relief liquor to waste.

3. In a hot acid system for digesting fibrous material, a digester, saiddigester having a side relief opening at a point below the top and abovethe bottom thereof, a high pressure accumulator, conduit means includinga pump for moving liquor from the high pressure accumulator into thedigester, means for returning liquor from the digester to the highpressure accumulator, a low pressure accumulator, a supply of acid,means including a low pressure eductor for moving acid from said supplyto said low pressure accumulator, a low pressure conduit line leadingfrom the top of the digester to the low pressure eductor, a side reliefstorage tank, a pipe line extending from said side relief opening intocommunication with the side relief storage tank, a degassing towerincluding a spray head in an upper portion thereof, means for pumpingthe side relief liquid and the contained gases from the side reliefstorage tank under pressure to said spray head, conduit means leadingfrom the top of said storage tank into communication with said lowpressure conduit line, a heat exchange device associated with the meansfor moving acid to the low pressure accumulator, means including avacuum pump for exhausting gas from said degassing tower and moving itthrough said heat exchange device, a reclaiming tower associated withthe acid supply, means guiding the cooled gas to said reclaiming towerfor absorption in the acid supply, means for guiding the side reliefliquor from the degassing tower to waste, and means for transferringheat units of the side relief liquor to the acid as it moves towards thelow pressure eductor.

4. In a hot acid system for digesting fibrous material, a digester, saiddigester having a side relief opening at a point below the top and abovethe bottom thereof, a high pressure accumulator, means for moving liquorfrom the high pressure accumulator into the digester, means for 7returningjthe liquor from the digester to the high pressure accumulator,a low pressure accumulator, a supply of acid, means including a lowpressure eductor for moving acid from saidsupply to said low pressureaccumulator, a low pressure conduit line leading from the top of thedigester to the low pressure eductor, a side relief storage tank, aconduit line extending from the side relief opening into communicationwith the side relief storage tank, a closed degassing tower including aspray head in an upper portion thereof, means for pumping liquor and thecontained gases from the side relief storage tank to said spray head, aconduit line leading from the top of said storage tank intocommunication with said low pressure line, heat transfer means in heatexchange relation with the means for moving acid to the low pressureaccumulator, means including a vacuum pump for exhausting gas from thedegassing tower and moving it through said heat transfer means, meansfor absorbing the cooled gas in said acid, means for guiding the siderelief liquor from the degassing tower to waste, and means fortransferring heat units of the side relief liquor to the acid movingtowards the low pressure eductor.

5. A method of digesting fibrous material which comprises, accumulatinga supply of digestion liquor in an accumulator, charging a digester withfibrous material,

moving liquor from the accumulator into the digester, cooking thefibrous material in the digester, venting side relief having a majorportion in a liquid phase from the digester at a point below the top andabove the bottom before completion of the cooking step, guiding the siderelief into a storage tank so that organic matter contained in the siderelief enters the storage tank and does not move into the accumulator,moving raw acid from a supply source to the accumulator, transferringheat units from the side relief liquor to the raw acid moving to theaccumulator, removing gas from the side relief, transferring heat unitsfrom the gas to the raw acid moving to said accumulator, absorbing saidreleased gas in said acid supply, and discharging the cooled side reliefliquor to waste.

6. A method of digesting fibrous material which comprises, storingdigesting liquor in an accumulator, charging a digester with fibrousmaterial, moving liquor from the accumulator into the digester, cookingthe fibrous material in the digester, venting side relief having a majorportion in the liquid state from the digester at a point below the topand above the bottom before termination of the cooking step, guiding theside relief into a storage tank separate from the accumulator so thatorganic matter contained in the side relief enters the storage tank,moving raw acid from a supply source to the accumulator tank, removinggas from the side relief, transferring heat units from the gas to theraw acid moving to said accumulator, absorbing said released gas in saidacid supply, and

discharging the side relief liquor to waste.

7. A method of digesting fibrous material which comprises, storingcooking liquor in an accumulator, charging the digester with fibrousmaterial, moving liquor from the accumulator into the digester, cookingthe fibrous material within the digester, venting side relief having amajor portion in a liquid state from the digester at a point below thetop and above the bottom thereof before termination of the cooking step,guiding the side relief liquor into a storage tank without deliveringsaid side relief into the accumulator, spraying the liquid side reliefunder pressure into a closed degassing tower to remove gases from theside relief liquor, moving acid from a supply source into theaccumulator, transferring heat units from said released gases to theacid moving to the accumulator, absorbing the cooled free sulphurdioxide component ofsaid gases in the supply of acid, discharging othercomponents of the gases to waste, transferring heat units of the siderelief liquor to the acid moving to the accumulator, and discharging thecooled degassed side relief liquor to waste.

8. A method of digesting fibrous material which comprises, storingsulphite liquor in an accumulator, charging the digester with fibrousmaterial, moving liquor from the accumulator into the digester, cookingthe fibrous material in the digester, venting side relief having a majorportion in a liquid state from the digester at a point below the top andabove the bottom thereof before termination of the cooking step, guidingthe side relief liquor into a closed storage tank without deliveringsaid side relief into the accumulator, moving acid from a supply sourceinto the accumulator, guiding sulphur dioxide released in said tank intoa position for absorption in said acid moving to the accumulator,spraying the liquid side relief under pressure into a closed degassingtower to remove gases from the side relief liquor, transferring heatunits from said released gases to the acid moving to the accumulator,absorbing the cooled free sulphur dioxide component of said gases in thesupply of acid, transferring heat units of the side relief liquor to theacid moving to the accumulator, and discharging the cooled degassed siderelief liquor to waste.

References Cited in the file of this patent UNITED STATES PATENTS1,263,486 Thornc Apr. 23, 1918 1,599,488 Richter Sept. 14, 19261,723,800 Michael et al. Aug. 6, 1929 1,804,967 Wolf et al May 12, 19311,908,615 Oman May 9, 1933 1,955,057 Dunbar Apr. 17, 1934 2,029,360 DeanFeb. 4, 1936 2,152,267 Merrill Mar. 28, 1939 2,165,644 Merrill et alJuly 11, 1939 2,205,374 Dunbar June 18, 1940 2,221,066 Kahle Nov. 12,1940 2,225,771 Dunbar Dec. 24, 1940 2,494,098 Lockman Jan. 10, 1950FOREIGN PATENTS 43,007 1 Norway July 26, 1926

1. IN APPARATUS FOR DIGESTING CELLULOSIC MATERIAL, A DIGESTER, ANACCUMULATOR, MEANS FOR MOVING COOKING LIQUOR FROM THE ACCUMULATOR INTOTHE DIGESTER, A SIDE RELIEF STORAGE TANK, A CONDUIT LINE EXTENDING FROMTHE DIGESTER FROM A POINT BELOW THE TOP AND ABOVE THE BOTTOM THEREOFINTO COMMUNICATION WITH THE SIDE RELIEF STORAGE TANK, A CLOSED DEGASSINGTOWER, A SPRAY HEAD IN A TOP PORTION OF SAID DEGASSING TOWER, MEANS FORPUMPING LIQUID AND THE CONTAINED GASES FROM THE SIDE RELIEF STORAGE TANKTO SAID SPRAY HEAD, A SUPPLY OF ACID, MEANS FOR MOVING ACID FROM SAIDSUPPLY TO THE ACCUMULATR, MEANS FOR TRANSFERRING HEAT UNITS FROM THE GASRELEASED IN THE DEGASSING TOWER TO THE ACID MOVING TOWARDS THEACCUMULATOR, MEANS FOR ABSORBING SUBSTANTIALLY ALL OF THE COOLED GASESIN THE ACID SUPPLY, MEANS FOR TRANSFERRING HEAT UNITS OF THE SIDE RELIEFLIQUID TO THE ACID SUPPLY, AND MEANS FOR DELIVERING THE COOLED ANDDEGASSED SIDE RELEF LIQUOR TO WASTE.